Conventionally, the disclosures in Japanese Patent Application Laid-Open (JP-A) No. 5-229015 for resin containers such as fuel tanks and the like mounted in automotive vehicles and methods for manufacturing the same have been known.
As shown in FIG. 36, in the method for manufacturing a resin container, firstly, a molten resin 122 in a high temperature state is extruded onto a convex metal mold 146 so as to conform to the measurements of the metal mold. Next, a vacuum is created in the suction holes 134 provided on an inner wall 132 of a concave metal mold 130 which corresponds to the shape of the convex metal mold 146 by a vacuum apparatus 140, and a film (a sheet member) 142 made of the same material as that of the resin 122 and having a gas barrier layer which prevents gasoline from permeating through is heated so as to adhere to the inner wall 132 of the concave metal mold 130. Then, the convex metal mold 146 and the concave metal mold 130 are die matched and heat compressed, and thereafter the molds are opened. The concave metal mold 130 holding an intermediate concave molded product formed in the above manner and kept in a high temperature state, and the other metal mold holding an intermediate concave molded product formed in the same manner and kept in a high temperature state are combined with each other and then are thermally compressed. Accordingly, the joint portions of the intermediate products adhere to each other in the high temperature state, so that the bonding strength is improved.
However, in the resin containers and the method for manufacturing the same mentioned above, when the seal members 142 are not securely die matched with each other in the bonding portions of the intermediate molded products, the level of gasoline permeability in the bonding portions is increased so that the gas permeation preventing performance is deteriorated. Accordingly, it has not been easy to obtain a resin container guaranteeing gas permeation prevention in the bonding portions.
In this case, the related art concerning the present invention includes Japanese Patent Application Laid-Open (JP-A) No. 63-260424 which discloses a fuel tank having a multi-layered resin structure, Japanese Patent Application Laid-Open (JP-A) Nos. 6-278223 and 6-278224 which disclose a fuel tank in which the peripheral portions of two concave resin containers is subjected to melt-adhesion, and Japanese Patent Application Laid-Open (JP-A) No. 58-202112 which discloses a fuel tank in which the peripheral portions of two containers comprising a resin layer and a metal foil are melted to adhere to each other.
Accordingly, the present invention takes the above facts into consideration and an object of the present invention is to provide a resin container and a method for manufacturing the same which can improve the gas permeation preventing performance in the bonding portions of intermediate molded products.
The present invention provides a resin container formed by superposing peripheral edge portions of at least two intermediate molded products, each of the intermediate molded products comprising at least two layers including a sheet member and a resin layer, in which the sheet members of the at least two intermediate molded products are melted and adhered to each other and the resin layers of the intermediate molded products are melted and adhered to each other. Accordingly, since the sheet members are securely adhered to each other in the bonding portion in which the peripheral edge portions of two intermediate molded products are superposed on each other, the gas permeation preventing performance in the bonding portion between the intermediate molded products can be improved.
Further, the present invention comprises an intermediate molded product forming step of forming concave intermediate molded products, each of the intermediate molded products comprising at least two layers including a sheet member and a resin layer, a sheet material melt-adhering step of superposing the peripheral edge portions of the intermediate formed products to melt and adhere the sheet members to each other, and a resin layer melt-adhering step of melt-adhering the resin layers of the intermediate molded products to each other. Accordingly, the resin container in which the gas permeation preventing performance in the bonding portion between the intermediate molded products is improved.